Today's theme is what we don't know. Scientists are staring out into the vastness of space and down at the tiniest particles, trying to figure out what the universe is made of.

Every time they think they're right, they're wrong.

Today's physics say that dark matter basically has to exist, but we're looking for it in obvious places, and we can't find it.

We're so mixed up about dark matter that Matthew Francis wonders whether cosmology is in shambles.

Whole new theories of space and time are coming out lately, but physicists wonder if "we're just too dumb" to figure them out.

Meanwhile, CERN is discovering new particles, which could send us straight back to the drawing board.

On the other end of the scale, we're looking for definitive images of supermassive black holes...

... and we're getting some tantalizing glimpses.

Image via Shutterstock.

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